Abstract
Currently, the existing local standards for the rebound method or industry standards recommended regression curves for the determination of the compressive strength of volcanic concrete often show significant errors, making it impossible to achieve the specified values, and thus failing to meet the acceptance criteria. This study conducts research and analysis on the correlation between compressive strength and rebound value of volcanic stone concrete. Through regression fitting and Pearson correlation coefficient analysis, it is found that there is a linear correlation between compressive strength and rebound value of volcanic stone concrete of different strength grades, and regression equations are obtained. According to the obtained regression equations to evaluate the volcanic concrete when the results obtained good, low error, for the corresponding specification modification put forward a guiding opinion, at the same time for the follow-up concrete related to the correlation between the compressive strength and rebound value of the correlation analysis provides guidance.
Abstract
The research aims to introduce a new device for determining the setting time of concrete by measuring surfacehardness and to prove its reliability. At the construction site, the setting time of the concrete is a critical point for concrete works, such as starting the surface finishing and starting the following works on the surface of the hardened concrete. The quality of finishing work for concrete surfaces is significantly related to setting time. Nevertheless, in an actual construction site, it is challenging to execute the current methods of evaluating the setting time of the placed concrete, such as the penetration resistance method of ASTM or other Non-destructive testing (NDT) methods. Therefore, in this research, based on the idea of measuring the hardness of materials, a settimeter (a combined word of setting time and meter), modified for concrete surface hardness measurement, was introduced, and evaluate the reliability under the various setting time conditions with retarding admixture and curing temperature. To evaluate the reliability of settimeter, the setting time of concrete mixtures was controlled with retarder and curing temperature. Compared with the current ASTM method of penetration resistance values, a settimeter showed similar timings of initial and final setting times with the penetration resistance test method. Finally, the experimental results obtained sufficient reliability with 0.82 of R^2 value between the settimeter and penetration resistance test values. Based on the research results, the suggested settimeter is expected to be a favorable method of determining the setting time of concrete on construction sites.
Key Words
concrete; penetration resistance test; setting time; settimeter; surface finishing work
Address
(1) Jong Kim, Min-cheol Han, Cheon-goo Han:
Department of Architectural Engineering, Cheognju University, 298 Daesung-ro, Cheongwon-gu, Cheognju 28503, Republic of Korea;
(2) Dongyeop Han:
Department of Architectural Engineering, Gyeongsang National University, 501 Jinju-daero, Jinju, 52828, Republic of Korea.
Abstract
The integration of manufactured sand into Ultra-High Performance Concrete (UHPC) remains limited, and the design methodology for UHPC mixes is not yet fully developed. This study proposes a semi-empirical gold tailings sand UHPC mix design method based on the Modified Andreasen and Andersen (MAA) model as an example of bulk solid waste gold tailings sand. This method compensates for the shortcoming of the unknown strength of the formulation when designing the mix using the MAA model. Also, it optimises the semi-empirical method of mix ratio design. The results of the study show that the method can be used to accurately obtain the unit amount of gold tailings sand and the rest of the raw materials in UHPC. Tests conducted on the slump flow, slump flow time, cubic compressive strength, and splitting tensile strength have demonstrated that the workability of the UHPC meets the required specifications, with the formulated mix's compressive strength deviating by less than 5%. At the same time, the gold tailings sand slightly reduce the fluidity of UHPC, while it has a positive effect on the compressive and tensile strengths. The compressive strength of UHPC with 28 days of gold tailings sand is improved by 4.57%, and the tensile strength is improved by 14.77%. In addition, the compressive strength of UHPC with 7 days of gold tailings sand is increased by 16.56% compared with that of the control group, indicating that the incorporation of gold tailings sand effectively improve the early compressive strength of UHPC.
Address
(1) Yuhao Jiao, Minghui Fan, Wenyuan Ren, Bo Zhang, Li Li:
College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China;
(2) Aijun Zhang:
College of Civil Engineering, Xijing University, Xi'an 710123, China.
Abstract
Sand is considered the most consumed natural resource after water. However, the world's sand deposits are depleting day by day due to their over-extraction for different industrial uses, which is becoming another sustainability threat. Incorporating and blending industrial waste to replace some constituent materials in concrete is becoming the new norm for environmental sustainability. This practice can benefit the construction industry and the environment at large. This investigation aims to study the durability properties of concrete produced with different industrial wastes as a partial replacement material for fine aggregate. Considerably, quarry dust and limestone dust were used to substitute the fine aggregate at different percentages (5%, 10% and 15%) and cured conventionally at 7, 28, 90 and 180 days. The durability properties of concrete were examined through water absorption, drying shrinkage, chloride and sulphate attack test and elevated temperature test. The experimental result shows that the optimum content of both quarry dust and limestone dust is 15% in terms of concrete durability. The durability performance of these materials indicates a significant filling effect which was obvious in the reduction of water absorption and dry shrinkage. Therefore, it is reasonable to utilize these materials as fine aggregate to produce concrete that is durable, economically feasible and environmentally sustainable.
Key Words
concrete durability; fine aggregate; limestone dust; quarry dust; waste materials
Address
(1) A. B. M. A. Kaish, Azrul A. Mutalib:
Department of Civil Engineering, Universiti Kebangsaan Malaysia, UKM Bangi 43600, Malaysia;
(2) Temple C. Odimegwu:
Department of Civil Engineering, Gregory University Uturu Abia State, PMB 1012 Amokwe Achara, Nigeria;
(3) Ideris Zakaria, Manal M. Abood:
Department of Civil Engineering, Infrastructure University Kuala Lumpur, Kajang 43000, Malaysia;
(4) Manal M. Abood:
Maricopa Community Colleges, 2411 W. 14th St., Tempe, Arizona 85281, USA;
(5) Asset Turlanbekov:
GCD Partner, Al Farabi Avenue 19, Almaty, Republic of Kazakhstan.
Abstract
The current fly ash-slag porous geopolymer formulations have low fly ash concentrations and limited porosity. Developing geopolymer porous materials with enhanced porosity is a key priority in advancing this field. One of the major challenges in producing thermomechanically stable, multifunctional composites is creating porous geopolymers (GC) that retain dimensional stability at elevated temperatures. This study examines the role of hydrogen peroxide decomposition in generating porosity in GC paste containing ceramic fillers such as cordierite and fireclay. To assess microstructural and porosity characteristics, digital microscopy, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were employed. For GC reinforced with fireclay and cordierite fillers, the viscosity values at a shear rate of 100 s-1 were 4.998 Pa.s and 4.227 Pa.s, respectively. The addition of these ceramic fillers resulted in an eightfold increase in apparent viscosity at 100 s-1 without compromising the material's pseudoplastic behavior. The yield stress exceeded 24.978 Pa, while cordierite fillers raised the plastic viscosity to over 5.895 Pa.s. The compressive strengths of the composite porous geopolymer mortars containing ceramic fillers ranged from 1.51 to 10.1 MPa, attributed to the high degree of interconnected porosity and large pore size within the matrix. In samples reinforced with cordierite, the formation of large, interconnected pores was strongly influenced by the curing rate. Thermomechanical analysis revealed that the porous geopolymer mortar reinforced with ceramic fillers exhibited excellent dimensional stability and minimal shrinkage (-1.5%) at 850°C. These findings suggest new pathways for developing GC composite porous mortars for diverse technological applications.
Key Words
cumulative intrusion; fireclay ceramics; pore volume; porous geopolymer; scanning electron microscopy
Address
(1) Nejib Ghazouani:
Civil Engineering Department, College of Engineering, Northern Border University, Arar 73222, Saudi Arabia;
(2) Abdellatif Selmi:
Prince Sattam Bin Abdulaziz University, College of Engineering, Department of Civil Engineering, Alkharj, 11942, Saudi Arabia;
(3) Abdellatif Selmi:
Ecole Nationale d'Ingénieurs de Tunis (ENIT), Civil Engineering, Laboratory, B.P. 37, Le belvédère 1002, Tunis, Tunisia
(4) Zeeshan Ahmad:
Department of Civil Engineering, Quaid-e-Azam College of Engineering and Technology (QCET) Sahiwal 57000, Pakistan;
(5) Bilal Ahmed:
Department of Structural Engineering, Faculty of Civil Engineering, Doctoral School, Akademicka 2, Silesian University of Technology, 44-100 Gliwice, Poland;
(6) Ahmed Babeker Elhag:
Department of Civil Engineering, College of Engineering, King Khalid University, PO Box 394, Abha 61411, Saudi Arabia;
(7) Ahmed Babeker Elhag:
Center for Engineering and Technology Innovations, King Khalid University, Abha 61421, Saudi Arabia.
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